实体框架6多对多想要插入重复的行 [英] Entity Framework 6 Many-to-many wants to insert duplicate rows

问题描述

应该不是这么难！我即将放弃EF ...



我的模特有每周报纸版。每个版本都可以有很多分类。每个分类可以出现在一个或多个版本中。我的型号：

  public   class 分类广告
 {
 [Key，DatabaseGenerated（DatabaseGeneratedOption.Identity）] 
  public   int  ClassifiedId { get ;  set ; } 
 ... 
  public   virtual  ICollection< EditionModel>版本{获取;  set ; } 
} 
 
  public   class  EditionModel 
 { 
 [Key，DatabaseGenerated（DatabaseGeneratedOption.None）] 
  public   int  EditionId {  get ;  set ; }  //  这是YYYYWW，WW =周数 
  public  DateTime PublicationDate { get ;  set ; } 
  public   virtual  ICollection< Classifieds>分类{{span class =code-keyword>获取;  set ; } 
} 

OnModelCreating覆盖：



< pre lang =c＃> protected 覆盖 void OnModelCreating（DbModelBuilder modelBuilder）
{
modelBuilder.Entity< EditionModel>（）
.Property（z = > z .EditionId）
.HasDatabaseGeneratedOption（DatabaseGeneratedOption.None）;

modelBuilder.Entity< EditionModel>（）
.HasMany（c = > c.Classifieds）
。 WithMany（d = > d.Editions）
.Map（x = >
{
x.MapLeftKey（ EditionId）;
x .MapRightKey（ ClassifiedId）;
x.ToTable（ EditionModelClassifieds）;
}）;
base .OnModelCreating（modelBuilder）;
}

创建分类广告操作代码（HTTP put）：

  public   async 任务< ActionResult>创建（分类分类， int  [] EditionList）
 {
  var  allPubs = PopulateEditionList（）;  //  当前和后续12个版本 
 classifieds.Editions = 新列表< EditionModel>（）; 
  foreach （ var  p  in  EditionList）
 {
  var  anEd =  new  EditionModel {EditionId = p} ; 
 db.Set< EditionModel>（）。Attach（anEd）; 
 classifieds.Editions.Add（anEd）; 
} 
 
 ... 
  if （ModelState.IsValid）
 {
 < span class =code-keyword> var  ads = db.Classifieds.Add（classifieds）; 
  await  db.SaveChangesAsync（）。ConfigureAwait（ false ）; 
  return 查看（ 收据，classifieds）; 
} 
 ... 
} 

提交新的分类广告后，我得到违反PRIMARY KEY约束'PK_dbo.EditionModels'。无法在对象'dbo.EditionModels'中插入重复键。



为什么EF坚持要求插入重复行EditionModels而不是仅仅将连接表行链接到其中的现有行？即使我选择了EditionModels中尚不存在的版本，我也会收到此错误。我如何解决这个问题？

解决方案

问题是EditionModel不是上下文的一部分。谢谢你，Slauma指出我正确的方向。更正的创建操作是：

 ... 
 classifieds.Editions =  new  List（）; 
  foreach （ var  p  in  EditionList）
 {
  var  ed =  await  db.EditionModel.FindAsync（ p）; 
  if （ed ==  null ）
 ed =  new  EditionModel {EditionId = p，PublicationDate =（ from  q  in  allPubs 其中 q.EditionId == p 选择 q）。单个（）。PublicationDate}; 
 InsertOrUpdate（ed）; 
 classifieds.Editions.Add（ed）; 
} 
 ... 

其余代码如上所示。

It shouldn't be this hard! I am about to give up on EF...

My model has weekly newspaper Editions. Each Edition can have many Classifieds. Each Classified can appear in one or more Editions. My models:

public class Classifieds
{ 
  [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
  public int ClassifiedId { get; set; }
  ...
  public virtual ICollection<EditionModel> Editions { get; set; }
}

public class EditionModel
{
  [Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
  public int EditionId { get; set; } // This is YYYYWW, WW = week number
  public DateTime PublicationDate { get; set; }
  public virtual ICollection<Classifieds> Classifieds { get; set; }
}

The OnModelCreating override:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
   modelBuilder.Entity<EditionModel>()
     .Property(z => z.EditionId)
     .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);

   modelBuilder.Entity<EditionModel>()
     .HasMany(c => c.Classifieds)
     .WithMany(d => d.Editions)
     .Map(x =>
     {
       x.MapLeftKey("EditionId");
       x.MapRightKey("ClassifiedId");
       x.ToTable("EditionModelClassifieds");
     });
   base.OnModelCreating(modelBuilder);
}

The Create Classifieds Action code (HTTP put):

public async Task<ActionResult> Create(Classifieds classifieds, int[] EditionList)
{
  var allPubs = PopulateEditionList(); // Current and next 12 editions
  classifieds.Editions = new List<EditionModel>();
  foreach (var p in EditionList)
  {
     var anEd = new EditionModel { EditionId = p }; 
     db.Set<EditionModel>().Attach(anEd);
     classifieds.Editions.Add(anEd);
  }

  ...
  if (ModelState.IsValid)
  {
     var ads = db.Classifieds.Add(classifieds);
     await db.SaveChangesAsync().ConfigureAwait(false);
     return View("Receipt", classifieds);
  }
  ...
}

On submit of a new Classifieds, I get "Violation of PRIMARY KEY constraint 'PK_dbo.EditionModels'. Cannot insert duplicate key in object 'dbo.EditionModels'."

Why does EF insist on wanting insert duplicate rows in EditionModels instead of just linking the junction table row to an existing row therein? I get this error even if I select an Edition which does not yet exist in EditionModels. How do I get around this?

解决方案

The problem was that EditionModel was not part of the context. Thank you, Slauma for pointing me in the right direction. The corrected Create Action is:

...
classifieds.Editions = new List();
foreach (var p in EditionList)
{
   var ed = await db.EditionModel.FindAsync(p);
   if (ed == null)
      ed = new EditionModel { EditionId = p, PublicationDate = (from q in allPubs where                      q.EditionId == p select q).Single().PublicationDate };
   InsertOrUpdate(ed);
   classifieds.Editions.Add(ed);
}
...

The rest of the code is as above.

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